What will this cam change do ?
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What will this cam change do ?
BBC 555 12.9 CR good heads (AFR 385) tunnel ram
Cam #1
erson 280 / 288 @ .050
.765 int / .731 lift ( had 1.8 rockers on intake valves so lift was more like .810)
112 LSA advanced to +4 IC (108)
Cam #2 (just installed this cam)
erson 286 / 296 @ .050
.808 int / .765 exh lift ( don't have any PV clearance to use the 1.8 rockers anymore so stick with the 1.7)
112 LSA advanced to +4 IC (108)
Cam #1
erson 280 / 288 @ .050
.765 int / .731 lift ( had 1.8 rockers on intake valves so lift was more like .810)
112 LSA advanced to +4 IC (108)
Cam #2 (just installed this cam)
erson 286 / 296 @ .050
.808 int / .765 exh lift ( don't have any PV clearance to use the 1.8 rockers anymore so stick with the 1.7)
112 LSA advanced to +4 IC (108)
Last edited by prairiehotrodder on Thu Apr 20, 2023 2:46 pm, edited 1 time in total.
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Re: What will this cam change do ?
What do you call good heads?
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Re: What will this cam change do ?
best heads i could afford. AFR 385
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Re: What will this cam change do ?
Well, since no one else is answering, I'll hazard a guess. I'm not a Chevy builder and have zero experience with that combination.
I would have to see the advertised durations so I could calculate overlap. A larger cam doesn't always make more power and a smaller cam doesn't always lose power. An engine needs a specific amount of camshaft overlap. Modern heads need less. Older, factory heads need more.
But my guess is that you may not see much difference at all. At some point, you can keep adding duration and it will do nothing because the heads are a choke point. You may have also added too much overlap for the combination. On engines this size (in Ford land anyway), a lot of the camshafts I use with durations in the 280 range at .050" duration will have a fairly long LSA, like 117-120°, because the advertised durations are up in the 3-teens and 320's and the heads just don't need a lot of overlap.
You *may* gain a few ponies due to the extra duration split and more lift, but I don't expect it to be a groundbreaking change. I could be wrong.
I would have to see the advertised durations so I could calculate overlap. A larger cam doesn't always make more power and a smaller cam doesn't always lose power. An engine needs a specific amount of camshaft overlap. Modern heads need less. Older, factory heads need more.
But my guess is that you may not see much difference at all. At some point, you can keep adding duration and it will do nothing because the heads are a choke point. You may have also added too much overlap for the combination. On engines this size (in Ford land anyway), a lot of the camshafts I use with durations in the 280 range at .050" duration will have a fairly long LSA, like 117-120°, because the advertised durations are up in the 3-teens and 320's and the heads just don't need a lot of overlap.
You *may* gain a few ponies due to the extra duration split and more lift, but I don't expect it to be a groundbreaking change. I could be wrong.
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www.customfordcams.com
Custom Ford Windsor, Cleveland, and FE Street/Race Engines
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Re: What will this cam change do ?
I don't think you will see much difference at all; maybe only a couple hundred more usable RPM up top.prairiehotrodder wrote: ↑Thu Apr 20, 2023 2:02 pm BBC 555 12.9 CR good heads (AFR 385) tunnel ram
Cam #1
erson 280 / 288 @ .050
.765 int / .731 lift ( had 1.8 rockers on intake valves so lift was more like .810)
112 LSA advanced to +4 IC (108)
Cam #2 (just installed this cam)
erson 286 / 296 @ .050
.808 int / .765 exh lift ( don't have any PV clearance to use the 1.8 rockers anymore so stick with the 1.7)
112 LSA advanced to +4 IC (108)
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Re: What will this cam change do ?
Post the combo,weight time slip shift points and DA you race in.
results speak for themselves
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Re: What will this cam change do ?
Could you explain your thoughts on why different heads need different overlap? Why do the older factory heads need more overlap compared to newer heads? Thanksblykins wrote: ↑Fri Apr 21, 2023 6:37 am Well, since no one else is answering, I'll hazard a guess. I'm not a Chevy builder and have zero experience with that combination.
I would have to see the advertised durations so I could calculate overlap. A larger cam doesn't always make more power and a smaller cam doesn't always lose power. An engine needs a specific amount of camshaft overlap. Modern heads need less. Older, factory heads need more.
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Re: What will this cam change do ?
Thanks for replying friends, A couple hp up top is about what we expected. I wasn't expecting anything big. One question : Does anyone know if removing the 1.8 rockers and going back to the 1.7 but still having the same valve lift because of the bigger cam will free up any hp due to reduced frictional losses ?
Brian
Brian
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Re: What will this cam change do ?
What was peak HP RPM with the old cam?
How high are you spinning the 555?
Is the tunnel ram modified?
I have followed this deal for a long time!
Good luck.
How high are you spinning the 555?
Is the tunnel ram modified?
I have followed this deal for a long time!
Good luck.
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Re: What will this cam change do ?
The motor has never been on a dyno. It will spin up to 7500 really quick though I'm not sure if there is any benefit up there. I was using the weiand street t-ram from the 80's but last year i switched to the slightly bigger weiand t-ram thats got more of an air-gap under the plenum. It helped so i know it wanted more flow. I would like to try the Edelbrock 7085 t-ram but i don't want to switch to dominators.
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Re: What will this cam change do ?
Post the combo,weight time slip shift points and DA you race in.
results speak for themselves
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- Posts: 1608
- Joined: Sat Dec 24, 2011 10:02 am
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Re: What will this cam change do ?
3100 pounds race ready
4.10 gears, 5500 stall
29 x 10 slicks
powerglide trans
Best time :
1.39 60 foot (nowhere near my best)
5.87 in the 1/8 at 119.75
9.166 at 148.01 1/4 mile
shift around 7100 - 7200
1500 feet elevation, air isn't usually very good.
4.10 gears, 5500 stall
29 x 10 slicks
powerglide trans
Best time :
1.39 60 foot (nowhere near my best)
5.87 in the 1/8 at 119.75
9.166 at 148.01 1/4 mile
shift around 7100 - 7200
1500 feet elevation, air isn't usually very good.
The Word of God is quick and powerfull
www.therocketshop.blogspot.com
www.therocketshop.blogspot.com
Re: What will this cam change do ?
Is that Weiand tunnel ram OTB? Not ported?
I would be measuring the intake plenum CSA and port exit CSA.
Some of those older tunnel rams need a fair bit of help with a grinder to make them work with large cubic inches and rpm.
Some had smaller CSA in the plenum than at port exit.
Measuring the CSA at different points will help determine what may or may not be required.
I would be measuring the intake plenum CSA and port exit CSA.
Some of those older tunnel rams need a fair bit of help with a grinder to make them work with large cubic inches and rpm.
Some had smaller CSA in the plenum than at port exit.
Measuring the CSA at different points will help determine what may or may not be required.
Re: What will this cam change do ?
Usually just due to a poor, less-flowing, inefficient port. Overlap lets the exhaust port scavenge the intake port.Old School wrote: ↑Sat Apr 22, 2023 8:52 amCould you explain your thoughts on why different heads need different overlap? Why do the older factory heads need more overlap compared to newer heads? Thanksblykins wrote: ↑Fri Apr 21, 2023 6:37 am Well, since no one else is answering, I'll hazard a guess. I'm not a Chevy builder and have zero experience with that combination.
I would have to see the advertised durations so I could calculate overlap. A larger cam doesn't always make more power and a smaller cam doesn't always lose power. An engine needs a specific amount of camshaft overlap. Modern heads need less. Older, factory heads need more.
This tends to be a mistake that I see a lot of guys make with newer style heads. They spec a cam with way too much overlap, which just puts the horsepower out the exhaust instead of converting it to power in the cylinder.
Lykins Motorsports
brent@lykinsmotorsports.com
www.lykinsmotorsports.com
www.customfordcams.com
Custom Ford Windsor, Cleveland, and FE Street/Race Engines
brent@lykinsmotorsports.com
www.lykinsmotorsports.com
www.customfordcams.com
Custom Ford Windsor, Cleveland, and FE Street/Race Engines